<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    body{
      height: 1000px;
    }
    div:nth-of-type(1){ /*绝对定位，相对于浏览器*/
      width: 100px;
      height: 100px;
      background: red;
      position: absolute;
      right: 0;
      bottom: 0;
    }
    div:nth-of-type(2){/*固定定位*/
      width: 50px;
      height: 50px;
      background: yellow;
      position: fixed;
      right: 0;
      bottom: 0;
    }
  </style>
</head>
<body>
<div id="father">
  <div id="first">div1</div>
  <div id="second">div2</div>
</div>
</body>
</html>